Computer Aided Draughting 403
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d:\N-Design\Des21-1.pm5
The co-ordinates can be input into the system by:
(i) The direct input of co-ordinate values in the respective order of x, y and z. If z co-
ordinate is not mentioned, then the values are assumed to be at a single given level.
(ii) Specifying the co-ordinates in an incremental format from the current cursor posi-
tion in the drawing area. The distance is specified by using @ parameter before the
actual values. The incremental values apply to all the ordinates.
(iii) Point co-ordinates may also be specified using the polar co-ordinate format. It can
also be an extension of the incremental format.
(iv) Using the mouse button, the cursor may be taken to the required position and the
button is clicked.
It is generally necessary to specify the limits of the drawing with the help of the command
LIMITS, where the user will be asked to specify the lower left corner and upper right corner of
the drawing sheet size. This establishes the size of the drawing.
21.7.2 Basic Geometric Commands
By way of choosing the basic commands in AutoCAD, one can make simple drawings. The
various entities that can be used for making an AutoCAD drawing in 2D are: point, line, ellipse,
polygon, rectangle, arc, circle, etc.
Generally AutoCAD provides a default option as <> in each of the command response.
The value shown in the angle brackets is the most recently set value. To have the same value,
one has to simply press the key. The various options available for each command are
shown in the command window. But the user need to respond by choosing one letter in most
cases, which makes the AutoCAD choose the right option.
21.7.3 Drawing Entity-POINT
The point command locates a point in the drawing.
Command: POINT (one has to give the location)
POINT: 25, 45 location of the point. Thus, a point is placed at the given location (25, 45).
After setting the limits of the drawing, the following drawing aids/tools may be used to
locate specific points on the screen (electronic drawing sheet).
ORTHO Command—this is orthogonal drawing mode. This command constrains the lines
drawn in horizontal and vertical direction only.
Command: ORTHO
ON/OFF :
SNAP Command—this command is used to set increments for cursor movement. If the
screen is on SNAP mode, the cursor jumps from point to point only. The cursor movement can
be effectively controlled using the SNAP command. This is useful for inputting the data through
digitizer/mouse.
Command: SNAP
Snap spacing or ON/OFF/Aspect/Locate/Style : 0.1 (default)
GRID Command-working on a plain drawing area is difficult since there is no means for
the user to understand or correlate the relative positions or straightness of the various objects
made in the drawing. The command enables to draw dotted lines on the screen at pre-defined
spacing. These lines will act as graph for reference lines in the drawing. The grid spacing can be
changed at will. The grid dots do not become part of the drawing.
Command: GRID
Grid spacing or ON/OFF/Snap/Aspect <0>: 0.5 (default)
